In a magnetic head suspension employed in a conventional hard disk drive (HDD), lead wires are used as a wiring arrangement to be connected to a magnetic head slider. It is noted, however, that, in recent hard disk drives (HDD), densification of recording density and miniaturization of units are quickly proceeded. Accordingly, the magnetic head slider is also miniaturized. By this, miniaturization and lowering load are also required for a magnetic head suspension serving as a plate spring for supporting a magnetic head slider used in HDDs. It is noted, however, that rigidity of lead wires disposed on the suspension becomes not negligible in accordance with reduction in load of such magnetic head suspension. Such rigidity may influence on the floating property of the magnetic head slider.
Under the circumstances, a suspension of an integrated wiring arrangement type is developed, in which a metal layer integrally formed with the suspension, rather than lead wires, is used as a wiring arrangement to be connected to the magnetic head slider.
FIG. 13 illustrates such suspension of an integrated wiring arrangement type. The suspension includes a load beam 1 and a flexure 2. A wiring arrangement 4 to be connected to a magnetic head slider (not shown) is integrally formed with the flexure 2. Specifically, the magnetic head suspension includes a load beam 1 of stainless steel having a thickness of 60-70 micrometers a flexure 2 of stainless steel having a thickness of 20-30 micrometers, and a base plate 3 of stainless steel having a thickness of 300 micrometers. The flexure 2 is spot-welded at a plurality of welds W to the load beam 1. The base plate 3 is also connected to the load beam 1 by welding. As shown in FIGS. 13 to 15(a), (b), (c), a polyimide layer 7 is formed on the upper surface of the flexure 2, i. e., on the surface of the flexure 2 opposite to the surface facing the load beam 1. Within the polyimide 7, wiring arrangement 4 of Cu (copper) having a thickness of about 5-10 micrometers, and pads 5 and 6 are formed. The magnetic head slider is attached to the flexure 2 at its distal region 9, and the terminal of the magnetic head slider is electrically connected to the pad 5.
FIG. 14 is a perspective view illustrating the suspension shown in FIG. 13 which has been disassembled into three parts, i. e., the load beam 1, the flexure 2 and the base plate 3. The magnetic head slider is adhesively attached to the region 9 to which it is to be attached. A load is applied to the magnetic head slider in the direction toward a disk, i.e.,in the vertical direction. Thus, the distal region of the load beam 1 adjacent to the base plate 3 is narrowed in a region of load bending 10 so as to have a predetermined resiliency, and is also bent into a predetermined configuration.
The sections respectively along line A--A, B--B and C--C in FIG. 13 are respectively shown in FIGS. 15(a), 15(b) and 15(c). As shown in these drawings, the polyimide layer 7 consists of an insulation layer 71 of polyimide having a thickness of 5-10 micrometers for providing electrical insulation between the wiring arrangement 4 and the flexure 2, and a protective layer 72 of polyimide having a thickness of 3-10 micrometers for covering the wiring arrangement 4 for protection thereof. It is noted that, as shown in FIG. 15(c), the protective layer of polyimide 72 has openings P disposed over the pads 6. Thus, the surface made of Cu of each of the pads 6 is exposed through a respective opening P. The protective layer 72 of polyimide disposed on the pad 5 has the same construction, although not specifically shown. The Cu surface of each of the pads 5 and 6 is often provided with Ni/Au plating, although not specifically shown.
A method for producing a magnetic head suspension according to prior art will be explained below.
FIGS. 16(a) to 16(e) are sectional views sequentially showing such production method. As shown in FIG. 16(a), an insulation film 171 of polyimide having a thickness of 5-10 micrometers and a Cu (copper) film 104 having a thickness of 5-10 micrometers are sequentially laminated on a stainless steel plate 102 having a thickness of 20-30 micrometers, subsequently constituting the flexure, in its entire surface. Then, a resist 11 is formed on the Cu film 104 in its wiring forming region. Thereafter, and as shown in FIG. 16(b), the Cu film 104 is etched away using the resist 11 as a mask, so as to form Cu wiring arrangement 4. Then, the resist 11 Is etched away , for example, by means of an organic solvent. Thereafter, and as shown in FIG. 16(c), a resist 12 is formed on the insulation film 171 of polyimide including the area where the Cu wiring arrangement 4 is formed. Then, the insulation film 171 of polyimide is etched away by means of hydrazine, for example, using the resist 12 as a mask.
The resist 12 is removed using an organic solvent, for example. Thereafter, and as shown in FIG. 16(d), photosensitive polyimide is applied on the entire surface. Then, exposure and development are performed so as to form the protective layer 72 of polyimide for covering the wiring 4. It is also possible to form the protective layer 72 of polyimide using non-photosensitive polyimide. It is noted, however, that, in such a case, a series of additional steps is required, such as application of non-photosensitive polyimide on the entire surface, formation of mask on the polyimide layer by means of resist, etching of the polyimide layer, and removal of the resist. Such series of additional steps may be obviated when the above-mentioned photosensitive polyimide is used, so that the process is simplified.
When the protective layer 72 of polyimide has been formed, a resist pattern 13 is formed on the opposite surfaces of the stainless steel plate 102 (subsequently constituting the flexure 2), as shown in FIG. 16(e). The stainless steel plate 102 is etched away using the above resist patterns 13, 13 as a mask, so as to form the flexure 2. Subsequently, the lower resist pattern 13 is removed using an organic solvent, for example. Thereafter, the flexure 2 is welded to the load beam 1. Then, the base plate 3 is welded to the load beam 1. The load beam 1 is further bent into a predetermined configuration, so that the magnetic head suspension shown in FIG. 15(a) is obtained.
In the conventional magnetic head suspension just mentioned above, the flexure 2 is attached to the load beam 1 by means of welding. Thus, strain due to the welding operation is introduced into the load beam 1 and the flexure 2. Accordingly, mechanical property (specifically, variation in the attitude angle of the flexure 2 at the region 9 where the magnetic head slider is attached thereto, and rigidity) of the load beam 1 and the flexure 2 is degraded, whereby reliability is reduced.
In the conventional method for producing a magnetic head suspension, the polyimide layer 7 and the Cu wiring 4 are formed on the stainless steel plate 102 which has been thinned to have a thickness of 20-30 micrometers in order to increase floating property of the magnetic head slider. Thus, the stainless steel plate 102 is easily deformed during the step of forming the polyimide layer 7 and the Cu wiring 4, whereby production yield is decreased.
According to prior art, and in order to stably perform various processes, such as photolithography, etching or the like relative to the thin stainless steel plate 102, the stainless steel plate is wound around a roll. The stainless steel plate is continuously unwound from the roll onto an equipment of each of the above-mentioned processes. The stainless steel plate output from each equipment is again wound around a roll each time after each process has been completed. In this connection, it is to be noted that, when the stainless steel plate 102 is wound around a roll, bowing or warping may be remained in the flexure 2 which has been formed by etching away the stainless steel 102. Thus, mechanical property of the flexure 2 is decreased (specifically, variation in the attitude angle of the flexure is increased), so that production yield is disadvantageously decreased.
It is further noted that each step or process requires a roll equipment in order to perform the unwinding and winding operations of the stainless steel plates this essentially requires a large production line. Equipment for transferring the stainless steel plate in rolled form is required between each process, so that the length of production line is also increased.